The overall objective is to use an experimental animal model system for understanding mechanisms relating to pathologic and immunologic events in infection of the human genital tract by organisms belonging to the Chlamydia group. The agent of guinea pig inclusion conjunctivitis (GP-ic) belonging to Chlamydia subgroup B will be used in male and female guinea pigs. The techniques employed will include conventional histopathology, immunofluorescence for detecting the agent in infected tissues and determination of immunoglobulins (IgG, IgM, IgA) in serum and secretions, electron microscopy, skin testing, and isolation of the agent from infected tissues. Immunization against genital infection will be attempted by inoculation of inactivated Gp-ic vaccine in the genital tract. In analyzing the immune response, infected and control animals will be treated with cyclophosphamide to determine the role of humoral antibody formation in recovery and immunity. The effect of antithymocyte serum will also be investigated to obtain information on the role of the cellular immune system. The effect of antibiotic therapy on recovery and subsequent immunity will be studied. Immunity to rechallenge, either by artificial or natural transmission, will be investigated in the female guinea pig. The influence of sexual maturity, sexual cycle, and hormones on genital infection will be investigated. Female guinea pigs following ovariectomy will receive estrogen and/or progesterone prior to inoculation with Gp-ic. Experiments to define the presence of chlamydiae in semen from male guinea pigs infected with Gp-ic will be performed. The development of a convenient animal model system with a subgroup A chlamydial organism will be undertaken using the agents of human lymphogranuloma cenereum and mouse pneumonitis in the genital tract of mice.